Field of the Disclosure
The present disclosure generally relates to a high performance subsea pressure regulator.
Description of the Related Art
A subsea pressure regulator regulates the pressure in a line and at the inlet to valves or other components downstream therefrom by either supply pressure from the accumulators therethrough, or dumping fluid to reduce pressure. Banks of subsea accumulators receive and store high pressure fluid that is produced by hydraulic pumps that are typically located topside, i.e. on a drilling platform at the ocean surface. The inlet port of the subsea pressure regulator is connected to the accumulator banks. A function circuit(s) is connected to the outlet, or regulated function port, of the subsea regulator. As the regulated function circuit(s) consumes pressurized fluid the regulator must respond quickly to open and maintain circuit pressure at the adjusted set point. The more quickly a subsea regulator can open and respond to a drop in regulated function circuit pressure, the more constant the circuit pressure that can be maintained.
Common subsea regulators must typically produce high flow rates to pressurize energized components while utilizing a seal set which consists of both a sliding metal vent seal(s) and a sliding metal supply seal(s). The vent seal is configured to prevent regulated pressure leaking into the vent circuit. This traditional subsea regulator sliding metal vent seal arrangement creates static and dynamic friction when the subsea hydraulic system requires regulated fluid to be supplied to the outlet side of the regulator. The metal vent seal creates a potential leak path through which pressure regulated fluid could leak and result in expensive repairs and wasted stored hydraulic energy which is potentially expensive in a subsea operating environment. Typically, the differential pressure across the metal vent seal is greater than the differential pressure across the metal supply seal. Each time the subsea regulator responds and opens to restore circuit pressure, the traditional metal vent seal needs to slide or cycle thereby creating unnecessary static and dynamic friction, unnecessary wear, and a potential leak path.
The significant increase in friction generated by the traditional metal vent seal has constrained the ability to regulate high pressure high flow rates subsea with the desired low “dead band”. Dead band is an industry term that describes the change in outlet pressure required to generate a dynamic response from the regulator. The traditional subsea regulator design results in a wide dead band which results in large variations in working pressures. Increased subsea operating depths and increased working pressures produce even wider dead bands due to the resulting increased differential pressure between the regulated pressure and the ambient subsea pressure.
Therefore, a need exists for a high performance subsea regulator which will minimize the characteristic dead band and produce a more constant regulated pressure.